This invention relates to fluid pumps of the oscillatory type and in particular but not exclusively relates to an electromagnetically operated oscillatory pump, although the pump of the present invention may be operated by other means. The invention also relates to one-way valves which are particularly suitable for such pumps but are also suitable for other uses.
French Certificat d'Utilite No. 2377140 and German Offenlegungsschrift No. 1550265 describe one-way valves with conical valve seats. While these valves provide improvements in the art, they have the disadvantage that because of the simple conical shape of the valve seats, the flexible valve members can tend to lift off the valve seats under high back pressure thereby allowing leakage. With this shape of valve seat, it is also necessary to have very small tolerances in the manufacture of the flexible valve member so that it fits very closely to the valve seat. These prior art valves are also designed for permanent stationary mounting and are not adapted nor appropriate for the rigorous conditions which pertain in dynamic situations such as with an oscillatory pump where the moving piston member is hollow and is fitted with a one-way valve.
The invention accordingly seeks to improve on these prior art constructions.
According to the invention there is provided a one-way valve comprising a housing defining a passageway therethrough, a valve seat located generally centrally of the passageway, and a generally annular flexible valve member secured at its periphery to the housing and extending over the valve seat, the member being arranged so that excess pressure across the valve member in one direction along the passageway causes the flexible member to extend away from the valve seat thereby permitting fluid flow in the said one direction, whereas excess pressure in the other direction urges the flexible member to seal against the valve seat thereby preventing fluid flow in the said other direction, the valve seat having a first surface portion which is generally conical and a second surface portion located radially inwardly of the first portion and extending generally parallel to the axis of the generally conical first portion, the valve member preventing flow by engagement with at least the second surface portion.
According to the invention there is also provided an oscillatory pump comprising a cylinder having inlet and outlet ends, a piston having a passageway therethrough and reciprocatable within the cylinder, the piston having a one-way valve arranged to open and close the passageway in the piston, and means for effecting reciprocatory movement of the piston whereby to pump fluid from the cylinder inlet to the cylinder outlet, the valve comprising a valve seat located generally centrally of the passageway, and a generally annular flexible valve member secured at its periphery to the housing and extending over the valve seat, the member being arranged so that excess pressure across the valve member in one direction along the passageway causes the flexible member to extend away from the valve seat thereby permitting fluid flow in the said one direction relative to the piston, whereas excess pressure in the other direction urges the flexible member to seal against the valve seat thereby preventing fluid flow in the said other direction relative to the piston.